This invention lies in the field of the measurement of the corrosive effect of fluid whether gases or liquids carried in pipelines. More particularly, this invention relates to an apparatus which can be attached to a pipeline and permits the introduction into and retrieval of a corrosion coupon from a pipeline, while the pipeline is under operating pressure.
It has been customary to determine the corrosiveness of a pipeline fluid so as to estimate the extent of corrosion to the interior surfaces of a pipeline, by inserting into the flowing fluid a coupon of metal of standardized size, shape, composition and finish. By visual inspection, or by measuring the loss of weight for a selected period of immersion in the fluid, the rate of corrosion can be determined. These coupons are generally inserted into the pipeline while the line is shut down, by removing a plug from the pipeline, inserting the coupon and then replacing the plug so as to seal the line against leakage.
A primary object of this invention is to provide an apparatus for inserting into and retrieving a corrosion coupon from the interior of a pipeline while the pipeline is operating and under fluid pressure.
It is a further object of this invention to provide a means of positioning a corrosion coupon inside a pipeline while the pipeline is under fluid pressure to precisely know the position of the coupon in the interior of the pipeline.
It is a still further object of this invention to support a corrosion coupon at a known position in the interior of a pipeline by means which electrically insulate the coupon from the pipeline structure, to minimize electrolyte corrosion.